1. Field of the Invention
The present invention relates in general to a carboxy-functional crosslinker composition comprising (i) 1,3,5-tris-(2-carboxyethyl)isocyanurate and/or a salt thereof, and (ii) a dicarboxylic acid crosslinking agent and/or a salt thereof. This invention also relates to curable compositions which produce durable, low-gloss films upon curing. In accordance with the present invention, the curable composition comprises, in its broadest concept, (i) a backbone resin component comprising a polyfunctional epoxy compound; and (2) a carboxy-functional crosslinker component comprising (i) 1,3,5-tris-(2-carboxyethyl) isocyanurate crosslinker and/or a salt thereof, and (ii) a dicarboxylic acid crosslinking agent and/or a salt thereof.
2. Description of the Related Art
Coatings prepared by curing polyepoxides with polybasic acid crosslinking agents (including the salts thereof) have been described in numerous references, including U.S. Pat. Nos. 3,730,930, 3,752,870, 3,781,380, 3,787,521, 4,181,642, 4,346,144, 4,650,718, 4,681,811, 4,703,101, 4,764,430, JP-A-61087767, JP-A-61087768, and JP-A-61087769, all of which are incorporated by reference herein as if fully set forth. One of the more common such polybasic acid crosslinking agents is 1,12-dodecanedioic acid. The coatings described in these references are said to have certain advantageous characteristics such as, for example, distinctness of image, good adhesion and high gloss.
U.S. Pat. No. 5,380,804 (also incorporated by reference herein as if fully set forth) describes liquid and powder coatings which employ 1,3,5-tris-(2-carboxyethyl)isocyanurate (hereinafter referred to as "TCI") as a polybasic acid (carboxy-functional) crosslinking agent for epoxy backbone resins. Films derived from the disclosed coatings are said to possess excellent hardness and resistance properties in comparison to films derived from commonly used carboxy-functional crosslinkers such as 1,12-dodecanedioic acid. The films are also described as possessing high gloss.
While hard, resistant, high gloss films are preferred for certain uses, such as automotive topcoats, a number of lower gloss applications for hard, resistant films also exist. It would, therefore, be highly desirable in these lower gloss end uses to benefit from the outstanding hardness and resistance properties imparted to crosslinked films by TCI.